AB1262 AMORPHOUS MINERALIZATION, CHONDROID AND/OR OSTEOID FORMATION IN CRYSTAL INDUCED METABOLIC DISORDERS – A COMPARATIVE STUDY OF APATITE RHEUMATISM, CHONDROCALCINOSIS AND PRIMARY SYNOVIAL CHONDROMATOSIS APATITE RHEUMATISM, CHONDROCALCINOSIS, PRIMARY SYNOVIAL CHONDROMATOSIS
Authors: Á. Apáthy, M. Bély
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Apatite rheumatism (<b>AR</b>), chondrocalcinosis (<b>Ch-C</b>) and primary synovialis chondromatosis (<b>prSynCh</b>) are calcium hydroxyapatite (<b>HA</b>) and calcium pyrophosphate dihydrate (<b>CPPD</b>) crystal induced progressive metabolic diseases, accompanied by more or less amorphous calcium phosphate [CaPO<sub>4</sub>], calcium carbonate [CaCO<sub>3</sub>]) deposits, chondroid and/or bone formation [1 – 5]. <h3>Objectives</h3> The <b>aim</b> of this study was. (1)to assess the mineralization, chondroid and/or bone formation of <b>AR</b>, <b>Ch-C</b> and <b>prSynCh</b> with conventional histologic stains and histochemical reactions, (2)to identify <b>HA</b> [Ca<sub>5</sub>(PO<sub>4</sub>)<sub>3</sub>(OH)] and <b>CPPD</b> [Ca<sub>2</sub>P<sub>2</sub>O<sub>7</sub>.2H<sub>2</sub>O] crystal deposits in conventionally fixed and stained tissue sections in comparison with unstained sections (Bély and Apáthy 2013) [6]. <h3>Methods</h3> <b>Ten</b> joints (6 knees, 1 hip, 3 shoulders) of <b>5</b> patients with <b>AR</b>, <b>16</b> joints (8 knees, 4 hips, 1 shoulder, 1 elbow, 2 wrists) of <b>16</b> patients with <b>Ch-C</b>, and <b>21</b> joints (14 knees, 5 hips, 2 elbows) of <b>20</b> patients with <b>prSynCh</b> were studied histologically. The amount of amorphous calcium phosphate and/or calcium carbonate deposits, furthermore chondroid and/or bone formation were evaluated by a semiobjective score system in conventionally stained tissue sections (<b>0</b> - no mineral deposits, chondroid and/or bone formation, <b>1</b> – minimal, <b>2</b> – moderate, and <b>3</b> – abundant). Standard stained and unstained tissue sections were examined with the light microscope and under polarized light, respectively. <h3>Results</h3> Summary of Patients' Demographics. The amount of amorphous calcium phosphate and/or calcium carbonate deposits was different in all patient groups; the average value of scores in tissue samples of patients with clinical diagnosis of <b>AR</b> was (1.80), with <b>Ch-C</b> (2.60), and with <b>prSynCh</b> (0.556). Chondroid formation in synovial membranes was minimal in tissue samples of patients with the clinical diagnosis of <b>AR</b> (0.058) or <b>Ch-C</b> (0.050); osteoid or bone formation was not detected (0.0). Massive chondroid formation (with or without osteoid or bone formation) was characteristic for <b>prSynCh</b> (2.1351). In tissue sections stained with <b>HE</b>, <b>HA</b> crystals were found only in <b>3</b> (<b>4.054</b> %), and <b>CPPD</b> in <b>15</b> (<b>20.27</b> %) of 74 tissue sections of <b>28</b> patients with the clinical diagnosis of <b>AR</b>, <b>Ch-C</b>, or with <b>prSynCh</b>. Using Bély and Apáthy's non-staining technique (2013), different amounts of <b>HA</b> and <b>CPPD</b> crystals were demonstrated in all <b>28</b> patients (<b>100</b> %) with the clinical diagnosis of <b>AR</b>, <b>Ch-C</b> and <b>prSynCh</b>. In unstained sections <b>HA</b> crystals were found in <b>49</b>, (<b>66.216</b> %), and <b>CPPD</b> in <b>44</b> (<b>59.459</b> %) of 74 tissue samples. The unstained sections were more efficient to demonstrate <b>HA</b> or <b>CPPD</b> crystals than conventionally stained ones. <h3>Conclusion</h3> Our study indicates that <b>AR</b>, <b>Ch-C</b> and <b>prSynCh</b> are crystal induced maladies and belong to the same group of metabolic diseases. All of these diseases start with <b>HA</b> and <b>CPPD</b> crystal deposition which provokes an inflammatory reaction. The inflammatory reaction is inhibited or moderated by calcium carbonate [CaCO3] and/or calcium phosphate [CaPO4] deposition in case of <b>AR</b> or <b>Ch</b>, and is inhibited or moderated by chondroid and/or osteoid formation in case of <b>prSynCh</b>. In our view <b>prSynCh</b> is a defect variant of metabolic disorders, characterized by diminished calcium phosphate and/or carbonate production. <h3>References</h3> [1]<b>Bély M, Apáthy A</b>: <i>Clinical Archives of Bone and Joint Diseases</i>, <b>2018</b>; 1.2 <b>DOI</b>: 10.23937/cabjd-2017/1710007 [2]<b>Bély M, Apáthy Á</b>: <i>Orvosi Hetilap</i>, <b>2013</b>; 154(23): 908-913. [Hungarian] <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> None Declared.